Conventionally, for a substrate of a semiconductor device, semiconductor single crystal such as high purity single crystal silicon and compound semiconductors such as gallium arsenic have been used mainly. As one of the semiconductor producing methods, a CZ method (Czochralski method) which pulls up a cylindrical ingot from a material melt in a crucible is known.
The CZ method first charges a raw material in the crucible within a chamber of a semiconductor ingot manufacturing apparatus and melts the material by heating by a heater disposed around the crucible. Seed crystal attached to a seed holder is contacted to the melt, and the seed holder is pulled up while rotating the seed holder and the crucible in the same direction or opposite directions to grow a cylindrical ingot having a prescribed size. Then, the ingot is sliced to produce thin silicon wafers which are to be used for semiconductor integrated circuits and the like (e.g., see Patent Literature 1).
FIGS. 6(A) and 6(B) show a semiconductor ingot manufacturing apparatus according to the CZ method. FIG. 6(A) is an explanatory view of a state that the seed crystal attached to the seed holder is contacted to the melt, and FIG. 6(B) is an explanatory view of a state that the seed holder is pulled up to grow an ingot.
In FIGS. 6(A) and 6(B), a semiconductor ingot manufacturing apparatus 1 is provided with a bottom-closed cylindrical chamber 2 and a cylindrical pull chamber 3 which is erected from the top center of the chamber 2.
The chamber 2 has within its furnace a crucible 4 which is formed of quartz having a bottom-closed cylindrical shape with an open top and a rotation shaft 7 of which top end is fixed to the bottom of the crucible 4. The bottom end of the rotation shaft 7 is connected to a drive source (not shown) outside of the chamber 2, and it supports to allow the rotations of the crucible 4 within the chamber 2. A heater 5 which surrounds the crucible 4 is disposed around the crucible 4, and a heat insulating material 6 is disposed to surround the exterior of the heater 5 to prevent radiant heat of the heater 5 from being directly radiated to the inside wall of the chamber 2.
A winding device 10 for a wire 9 is disposed on the top of the pull chamber 3. A seed holder 12 is attached to the tip end of the wire 9 via a coupling member 11. The coupling member 11 hangs a hopper (not shown) for replenishing a raw material in charging and recharging steps and hangs the seed holder 12 to which the seed crystal is attached in a step of pulling up an ingot 13. A gate valve 14 for separating the interior of the pull chamber 3 into upper and lower sections is disposed close to the lower part of the pull chamber 3.
In the structure described above, the raw material is charged in the crucible 4 which is disposed within the chamber 2 and melted to prepare a silicon melt 8 by heating to melt the material by radiant heat of the heater 5 which is disposed to surround the crucible 4. Then, the seed crystal attached to the seed holder 12 is contacted to the silicon melt 8, and the ingot 13 is grown by pulling up the seed holder 12 by driving the winding device 10 while the seed holder 12 and the crucible 4 are rotated in the same direction or opposite directions.
Patent Literature 1:
Japanese Patent Application Laid-Open No. 8-261903